E320 W124 ABS light stays on
MBWorld Fanatic!
Joined: Nov 2002
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From: Massachusetts
2018 GLE350, 2014 G550, 2000 SL500, 1980 TR8, 1995 E320 Cabriolet
Here is a troubleshooting guide that may help. You cannot read ABS codes on the 8 or 16 pin diagnostic connectors on the 4 & 6 cylinder W124 cars, however, you can read them on the 38 pin connector on the V8 models.
- FD
- FD
MBWorld Fanatic!
Joined: Nov 2002
Posts: 1,028
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From: Massachusetts
2018 GLE350, 2014 G550, 2000 SL500, 1980 TR8, 1995 E320 Cabriolet
Phat -
I noted that your profile says you drive a 400e, but the title of your post simply says E320 W124, so I am assuming that we're talking about a a 6 cylinder car here. I have posted the diagnostic connector functional pin outs for 8, 16, and 38 pin connectors. On the 8 or 16 pin connectors, pin 6 is the SRS (Airbag) pulse code output which will not be relevant to an ABS problem. Pin 6 is, however, the ABS output on your 400e which will have the 38 pin connector.
Follow the troubleshooting guide in the PDF and see what you come up with.
- FD
I noted that your profile says you drive a 400e, but the title of your post simply says E320 W124, so I am assuming that we're talking about a a 6 cylinder car here. I have posted the diagnostic connector functional pin outs for 8, 16, and 38 pin connectors. On the 8 or 16 pin connectors, pin 6 is the SRS (Airbag) pulse code output which will not be relevant to an ABS problem. Pin 6 is, however, the ABS output on your 400e which will have the 38 pin connector.
Follow the troubleshooting guide in the PDF and see what you come up with.
- FD
Thread Starter
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mercedes 400e
Hi Floobydust,
Thank you so much for the information. I am still digesting the Mitchell information you sent. Indeed, I have the 400e with 300K miles on it. I recently got a 320. I wish I can get the ABS tester to do the job right.
Phat
Thank you so much for the information. I am still digesting the Mitchell information you sent. Indeed, I have the 400e with 300K miles on it. I recently got a 320. I wish I can get the ABS tester to do the job right.
Phat
MBWorld Fanatic!
Joined: Nov 2002
Posts: 1,028
Likes: 133
From: Massachusetts
2018 GLE350, 2014 G550, 2000 SL500, 1980 TR8, 1995 E320 Cabriolet
phat -
Two more suggestions. One, be sure that all of your fuse contacts are cleaned and that the fuses are each removed and inspected (preferably replaced). Two, check your OVP relay - if you are not familiar, it is located behind the battery and has one or two blade style fuses located under a plastic cover on it. Be sure that (those) fuse(s) is(are) not blown. The OVP supplies power to the ABS solenoid relay and no-power to this relay is what causes the ABS light to come on (via a blocking diode).
- FD
Two more suggestions. One, be sure that all of your fuse contacts are cleaned and that the fuses are each removed and inspected (preferably replaced). Two, check your OVP relay - if you are not familiar, it is located behind the battery and has one or two blade style fuses located under a plastic cover on it. Be sure that (those) fuse(s) is(are) not blown. The OVP supplies power to the ABS solenoid relay and no-power to this relay is what causes the ABS light to come on (via a blocking diode).
- FD
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Thread Starter
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mercedes 400e
Hi
My other E320 has a different ABS problem. the ABS light will come on after about 20ft of driving. It is consistent. I have checked the front speed sensors. They have 1600 Ohms, and they generate AC current when the wheels are turned. The rear sensor has 700 Ohms, I have not checked the current yet. This is the car that I borrowed the ABS module from. So the module works OK but somehow it gives ABS light when driving. Thank you in advance
My other E320 has a different ABS problem. the ABS light will come on after about 20ft of driving. It is consistent. I have checked the front speed sensors. They have 1600 Ohms, and they generate AC current when the wheels are turned. The rear sensor has 700 Ohms, I have not checked the current yet. This is the car that I borrowed the ABS module from. So the module works OK but somehow it gives ABS light when driving. Thank you in advance
MBWorld Fanatic!
Joined: Nov 2002
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From: Massachusetts
2018 GLE350, 2014 G550, 2000 SL500, 1980 TR8, 1995 E320 Cabriolet
This could be because the output of one of the wheel sensors is dropping below the minimum threshold voltage that is necessary to "read" the sensor. MB uses a variable reluctance type sensor on which the voltage output is proportional to wheel speed and the distance between the end of the sensor and the teeth on the hub (the magnetic circuit length). Note that the sensor output voltage is not used to determine the wheel speed (the pulse rate is), but a minimum voltage is required for the internal circuitry (a Schmidt trigger) to detect pulses (this is tested during the BITE test). The BITE test cycle begins when wheel speed in all 3 speed channels exceeds 3 MPH. The test cycle is activated by speed sensor voltage.
If the sensors or hub teeth are dirty, the signal amplitude can be reduced. If there is excessive wheel bearing play, braking forces can pull the hub teeth away from the sensor, increasing the magnetic path length, and potentially lowering the output voltage below the threshold voltage. At low speeds, there is not enough braking force to disturb the path leng
I would:
- Clean the front sensors and the teeth on the hub
- Check/adjust the wheel bearing play
- Inspect the plastic on the ends of the front sensors - replace sensor if it is worn through (can allow moisture in and can allow metal-metal contact with the hub teeth which can distort the output)
- FD
If the sensors or hub teeth are dirty, the signal amplitude can be reduced. If there is excessive wheel bearing play, braking forces can pull the hub teeth away from the sensor, increasing the magnetic path length, and potentially lowering the output voltage below the threshold voltage. At low speeds, there is not enough braking force to disturb the path leng
I would:
- Clean the front sensors and the teeth on the hub
- Check/adjust the wheel bearing play
- Inspect the plastic on the ends of the front sensors - replace sensor if it is worn through (can allow moisture in and can allow metal-metal contact with the hub teeth which can distort the output)
- FD
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mercedes 400e
The front sensors have metal shows thru. Is this normal? How can I clean the teeth? They are kind of buried. The wheel bearing are good, no play at all. This car was flooded though. Maybe the teeth are rusted? Thank you so much for your advise
Phat
Phat
MBWorld Fanatic!
Joined: Nov 2002
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From: Massachusetts
2018 GLE350, 2014 G550, 2000 SL500, 1980 TR8, 1995 E320 Cabriolet
Flood cars can be really dicey - you never know what the water got into. Even if you get everything working, corrosion works away on things and the car becomes a rolling bag of intermittent problems. But I digress . . . .
No, there should be no metal showing. The sensors are designed to be sealed so that water can't get in and short corrode things. Add this to the flood status, and I would say the sensors are very suspect, even if the resistance measures okay. A few shorted windings can really reduce the voltage output while still measuring okay on a DC resistance test.
The wear of the plastic covering occurs when the gap between the sensor and the hub teeth gets too small. The two causes that I know of are excessive wheel bearing play or foreign material building up on the hub teeth or sometimes the sensor. Again, the flood history may come into play as the hub teeth may be severely corroded. Even if the sensor is still good, the excess iron oxide between the teeth will significantly reduce the voltage output from the sensor.
I would start be inspecting/cleaning the hub teeth. The only way I know to do that is to remove the caliper, rotor, and hub. Once you have the hub off, use a wire wheel to clean up the teeth. Then see what happens. If you still have the problem, I would then suspect the sensors.
- FD
No, there should be no metal showing. The sensors are designed to be sealed so that water can't get in and short corrode things. Add this to the flood status, and I would say the sensors are very suspect, even if the resistance measures okay. A few shorted windings can really reduce the voltage output while still measuring okay on a DC resistance test.
The wear of the plastic covering occurs when the gap between the sensor and the hub teeth gets too small. The two causes that I know of are excessive wheel bearing play or foreign material building up on the hub teeth or sometimes the sensor. Again, the flood history may come into play as the hub teeth may be severely corroded. Even if the sensor is still good, the excess iron oxide between the teeth will significantly reduce the voltage output from the sensor.
I would start be inspecting/cleaning the hub teeth. The only way I know to do that is to remove the caliper, rotor, and hub. Once you have the hub off, use a wire wheel to clean up the teeth. Then see what happens. If you still have the problem, I would then suspect the sensors.
- FD
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mercedes 400e
I cleaned the teeth both sides today. They look perfect when done. Bearings are good. ABS light still comes on right away. I noticed that the metal is showing on both sensors. They must be bad? I have another E320 that has no issues. Should I borrow the sensors to test or is it too risky to open a new can of worm?
MBWorld Fanatic!
Joined: Nov 2002
Posts: 1,028
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From: Massachusetts
2018 GLE350, 2014 G550, 2000 SL500, 1980 TR8, 1995 E320 Cabriolet
Swap the sensors - easy and quick. There is no electrical risk with this. Once you have the swapped sensors in place, rotate the hubs to make sure you don't have any binding (e.g., the hub teeth hitting the end of the sensors). See if you are good to go.
- FD
- FD
